The basic purpose of this work is to study the accessibility and relative rotational freedom of paramagnetic spin labels in the channels of tooth enamel and by these studies to learn something of the role of the aqueous phase in tooth enamel. Magnetic resonance studies will be employed to study both diffusing small spin labels as well as labels covalently bound to the organic matrix. Observation of anisotropically rotating probes will be correlated with the directional properties of the oriented enamel crystallites by way of oriented sample studies.